Hydraulically elevatable platforms

ABSTRACT

Access equipment of the kind comprising an articulated boom structure which consists of a first boom pivotally and preferably rotatably mounted on a vehicle or like supporting structure, and at least one further boom pivotally connected to the free end of the first boom, hydraulic actuating cylinders being provided for effecting relative pivotal movement of the booms one to the other, and both to the supporting structure, means being associated with each boom and movable therewith for transmitting movements of the booms individually and collectively to a plurality of stops which are thus movable to actuate control valves for the hydraulic actuating cylinders, the stops being arranged in response to movements of the booms and in accordance with permitted degrees of pivotal movement thereof to arrest operation of the actuating cylinders as appropriate to prevent the boom structure assuming a potentially unstable configuration.

States atent n91 Unite Ashworth [111 3,891,056 1 June 24, 1975 DenisHenry Ashworth, Dudley, England [73] Assignee: Simon Engineering DudleyLimited, Cheshire, England 22 Filed: Feb. 7, 1974 211 Appl. No.: 440,552

[75] Inventor:

Primary Examiner-Reinaldo P. Machado Attorney, Agent, or FirmNorris andBateman 5 7] ABSTRACT Access equipment of the kind comprising anarticulated boom structure which consists of a first boom pivotally andpreferably rotatably mounted on a vehicle or like supporting structure,and at least one further boom pivotally connected to the free end of thefirst boom, hydraulic actuating cylinders being provided for effectingrelative pivotal movement of the booms one to the other, and both to thesupporting structure, means being associated with each boom and movabletherewith for transmitting movements of the booms individually andcollectively to a plurality of stops which are thus movable to actuatecontrol valves for the hydraulic actuating cylinders, the stops beingarranged in response to movements of the booms and in accordance withpermitted degrees of pivotal movement thereof to arrest operation of theactuating cylinders as appropriate to prevent the boom structureassuming a potentially unstable configuration.

11 Claims, 4 Drawing Figures PATENTEDJlm24 1975' 3.891; 056

SHEET 1 HYDRAULICALLY ELEVATABLE PLATFORMS This invention concernsaccess equipment of the kind (hereinafter termed of the kind referredto) comprising an articulated boom structure consisting of a first boompivotally and preferably rotatably mounted on a vehicle or likesupporting structure, and at least a second boom pivotally connected tothe free end of said first boom, hydraulic actuating cylinders beingprovided for effecting pivoting movement of the second boom relative tothe first and both booms relative to the supporting structure.

It is essential to ensure that relative movement of the booms does notcreate a potentially unstable condition, i.e., when a vertical line fromthe combined centres of gravity of the various parts of the boomstructure falls outside the area occupied by the supporting structure.In order to avoid such instability it is necessary to limit the degreeof movement of each boom according to said area and to the position ofone or more of the other booms.

Furthermore, it is considered important to ensure that movement of anyboom is not suddenly arrested at its permitted limit, or at the ends ofthe stroke of the hydraulic actuating means.

An object of the invention is to provide access equipment of the kindreferred to, wherein movement of the booms into a potentially unstablecondition is prevented, and preferably wherein permitted movements areprogressively retarded to prevent sudden arrest thereof at the permittedlimits.

According to the present invention, there is provided access equipmentof the kind referred to, wherein means are associated with each of saidbooms and movable therewith for transmitting movements thereofindividually and collectively to stops which are movable to actuatecontrol valves for said hydraulic actuating cylinders, said stops thusbeing arranged in response to movements of said booms and in accordancewith permitted degrees of pivotal movement thereof to arrest operationof said actuating cylinders as appropriate to prevent the boom structureassuming a potentially unstable configuration.

An embodiment of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings, in which:

FIGS. 1 and 2 show schematically a boom structure in two operationalpositions;

FIG. 3 is an elevation of a link system connected to said boom structureand having stop means in accordance with the invention;

and FIG. 4 is a plan view of the arrangement shown in FIG. 3.

Referring now to FIGS. 1 and 2, an articulated boom structure comprisesin this case two main booms l and 11 hereinafter referred to as firstand second booms respectively, and a shorter auxiliary boom 12 having acage or working platform 13 pivotally mounted at the outermost endthereof. The lowermost or innermost end of the first boom is pivotallymounted on a turntable 9 for rotation relative to a supporting structuresuch as a vehicle (not shown).

A parallelogram linkage system is provided for maintaining the cage 13level for all positions of the boom structure. This system comprisesthree levelling rods 14, 17 and 19 forming parallelograms respectivelywith said first, second and auxiliary booms.

Actuating means comprising hydraulic cylinders 20 and 20a are providedfor elevating the first boom relative to the turntable 9 and the secondboom relative to the first. The cylinder 20a operates a rod 21 connectedto the second boom, a rod 22 being pivotally connected at one end to therod 21 part way along its length, and at the other end to said firstboom 10. The cylinder 20, rod 21 and rod 22 are positioned along thelongitudinal centre line of the boom structure. A pivot shaft 23 towhich the rod 22 is attached extends outwardly through the wall of theboom 10 and has attached to one end a first connecting link 24. A secondconnecting link 25 is pivotally attached to the link 24 and extends backalong the side of the boom 10 towards the turntable 9. The end of thelink 25 remote from the link 24 is pivotally connected to one end of acommon link 26, the other end of which is pivotally connected to thelower levelling rod 14 associated with the boom 10.

It will be appreciated that upwards or downwards movement of the secondboom 11 is transmitted to the common link 26 via rod 2], rod 22, shaft23, connecting link 24 and connecting link 25, and that upwards ordownwards movement of the first boom 10 is transmitted to the commonlink 26 via the lower levelling rod 14.

Referring now to FIGS. 3 and 4, a driving link 27 pivotally connected atone end to the upper end of the common link 26 is connected at its otherend to a driving arm 28. The arm 28 is pivotally mounted at its lowerend on a shaft 30 attached to the boom 10, and carries strikingabutments 29 and 29a adjacent the shaft 30.

Also, pivotally connected to the link 26 at approximately its mid-point,is one end of a further driving link 31 which, at its other end, isconnected to a further driving arm 32 part way along its length. The arm32 is also pivotally mounted on shaft 30, and there is a correspondingdriving arm 32a spaced therefrom and pivotally mounted on a shaft 33also attached to boom 10. Interconnecting the upper ends of the drivingarms 32, 32a is a rod 34 which carries four stops or strikers A, B, Cand D.

A further pair of driving arms 35 and 36 pivotally mounted on shaft 30and ashaft 37 respectively are interconnected at their upper ends by arod 38 which carries two further stops or strikers E and F spaced apartalong its length.

A still further pair of driving arms 39 and 40 are pivotally mounted onshafts 37 and 33 respectively, and are interconnected at their upperends by a rod 41 which carries two further stops or strikers G and Hspaced apart along its length.

Driving arms 36 and 39 are normally retained in the positions shown inFIGS. 3 and 4 by springs 42.

The driving arms 28, 32, 32a, 35, 36, 39 and 40 are all separately andfreely rotatable on their associated shafts 30, 33 and 37.

Two further abutments X and Y are mounted in spaced apart relationshipdirectly on levelling rod 14 and extend into the line of pivotingmovement of the arm 39.

The strikers A to H, all of which are preferably adjustable in positionon their respective rods for the purpose of setting up the apparatus,are operatively disposed adjacent control levers and 51 pivotallymounted respectively on shafts 52 and 53, and adapted to actuate thehydraulic cylinders for raising and lowering the first and second boomsrespectively. Movement of the lever 50 to the left and right in FIG. 4causes the first boom to be lowered and raised respectively. Movement ofthe lever 51 to the left and right in FIG. 4 causes the second boom tobe raised and lowered respectively.

The system so far described is adapted to ensure that the boom structurecan never be moved into a potentially unstable condition, such as wouldbe created when a vertical line from the combined centres of gravity ofthe parts of the boom structure falls outside an area bounded by thesupporting structure, which latter normally comprises a vehicle havingstabilising jacks.

The positions of the parts as shown in FIGS. 3 and 4 is for a conditionwhen both booms l and 11 are in a stowed position, i.e., both horizontaland in superimposed relationship.

If the second boom 11 is raised, with the first boom remaining in ahorizontal position, the lever 51 being at its left hand limit ofmovement, the connecting link 25 attached indirectly to the rod 22 ismoved to the right in FIGS. 3 and 4. If the lower boom is stationary thelevelling rod 14 is also stationary so that the link 26 is pivoted in aclockwise direction causing links 31, arms 32 and 32a, rod 34 and stopsA, B, C and D all to move to the right. The relative dimensions of thevarious moving parts of the system are so arranged that, as the secondboom 11 approaches its permitted limit of elevation, the stop C on therod 34 contacts the control lever 51, returning it gradually to acentral position, and thus retarding and finally arresting elevation ofthe boom.

If the first boom 10 is raised, the lever 50 being at its right handlimit of movement, the lower levelling rod 14 is moved to the left. Thelink 26 thus pivots in a clockwise direction about its upper end,causing the stop C to move away from control lever 51, allowing furtherelevation of the second boom 11 if required. If the first boom 10approaches a position causing the second boom 11 or auxiliary boom 12 orcage 13 to contact the ground or platform mounting, the stop B on rod 34contacts the control lever 50 returning it once again gradually to acentral position. Further elevation of the second boom, however, movesstop B away from control lever 50, thus allowing further elevation ofthe first boom if required.

It will be seen, therefore, that the combined movements of the two boomsare transmitted by link 26 to the rod 31 which, according to theconditions prevailing, move stops A, B, C and D towards or away fromcontrol levers 50 and 51 to maintain a stable condition of the boomstructure, thus stop A controls downward movement of the lower boom 10,and stop D controls downward movement of the upper boom 11, asnecessary.

Stops A, B, C, and D serve as described to control the degree ofmovement of booms 10 and 1 l to within safe limits and to retard suchmovement as the booms approach said limits. The remainder of the system,now to be described, serves, on the other hand, to retard movement ofthe booms as they approach limits determined by the stroke of thehydraulic actuating cylinders.

As the second boom is raised link 25, rod 27 and arm 28 move to theright. After a period of such movement the abutment 29 near the base ofthe arm 28 abuts arm 35 moving the latter, together with arm 36, to theright with continued movement of the arm 28. Assuming the second boom ispermitted by stop C to reach its normal limit of elevation, determinedby the stroke of the cylinder 20a, as the boom approaches thiscondition, the stop E on rod 38 contacts control lever 51, graduallymoving same towards its central position, thus elevation of the boom isretarded and finally arrested. When this condition is relieved bylowering of the second boom, and abutment 29 eventually moves away fromarm 35, the latter, together with arm 36, is caused to return to theposition shown in FIGS. 3 and 4 by one of the pairs of springs 42.

As the first boom 10 is raised the lower levelling rod 14 is moved tothe left until the boom approaches its normal limit of elevationdetermined by the stroke of the actuating cylinder, whereupon stop Y onlevelling rod 14 contacts arm 39, moving same to the left, thus stop Hcontacts control lever 50 and gradually moves same towards its centralposition, which serves to retard and finally arrest elevation of thefirst boom. When this position is relieved by lowering the first boom,stop Y releases arm 39, which together with arm 40, is returned to itsoriginal position by the other pair of springs 42.

If the first boom is lowered towards its stowed position on the vehicle,as it approaches this position stop X contacts and moves arm 39 so thatthe action of stop G slows down and finally arrests movement of thefirst boom by contacting control lever 50 and moving same gradually toits central position.

If the second boom is lowered towards its stowed position insuperimposed relationship with the first boom on the vehicle, as itapproaches this position the abutment 29a contacts arm 35 moving same tothe left in FIGS. 3 and 4. Thus, the stop F on rod 38 contacts controllever 51 and gradually moves same to its central position which servesto retard and finally arrest movement of the second boom.

The assembly illustrated in FIGS. 3 and 4 is housed within a casing 45on the first boom 10, which also houses the control levers 50 and 51which are manually operable, duplicate controls being provided in thecage 13. Operation of the duplicate controls causes actual movement ofthe main control levers 50 and 51, which therefore ensures that thesafety system operates when the boom structure is moved by an operator,whether in the cage or at the base. In some cases, an over-ride featureis provided which enables cancellation of the ability to controlmovement of the booms from the cage. However, the safety system islinked to the base controls and therefore remains operative at alltimes.

It is not intended to limit the invention to the above example only,many variations, such as might readily occur to one skilled in the art,being possible without departing from the scope of the invention.

Furthermore, in the arrangement described in relation to the drawings,movements of the second boom may be transmitted from the boom itself orany part or parts which move with the boom. However, it is preferable toutilise the rod 22 for this purpose as it moves through a smaller anglethan the second boom, although its movement remains proportional to thatof the latter. This smaller angle of movement is approximately equal tothat moved by the first boom, so that both ends of the common link movethrough a similar angle, thus avoiding a complex construction of thelink in order to combine the movements transmitted from both booms.

What is claimed is:

1. Access equipment comprising an articulated boom structure comprisinga first boom pivotally mounted at one end on a vehicle or likesupporting structure and at least a second boom pivotally connected tothe free end of said first boom, hydraulic actuating cylinders connectedfor effecting pivoting movement of the second boom relative to the firstboom and both booms relative to said supporting structure, controlvalves for said cylinders, movably mounted stops for controllingactuation of said valves, and means associated with each of said boomsand movable therewith for transmitting movements thereof individuallyand collectively to said stops to actuate said control valves, saidstops being so arranged that in response to movements of said booms andin accordance with permitted degrees of pivotal movement thereofoperation of said actuating cylinders is controlled as appropriate toprevent the boom structure assuming a potentially unstableconfiguration.

2. Access equipment according to claim 1, wherein said means comprise apair of members each reciprocable substantially linearly in response toclockwise and anti-clockwise pivoting movements respectively of itsassociated boom, said stops being carried by a further member alsomovable substantially linearly and operatively connected to said pair ofmembers, the position of said further member being at all timesrepresentative of the combined linear positions of said pair of members.

3. Access equipment according to claim 2, wherein the members of saidpair are adapted for relative movement in opposite directions uponsimultaneous raising or lowering of both of said booms, said furthermember being pivotally connected to a common member extending betweenand pivotally connected to said pair of members, such that movements ofsaid further member are at all times representative of the sum of themovements of said pair of members.

4. Access equipment according to claim 1, wherein said means are somovable with said booms that movements thereof are transmitted tofurther stops which are movable to actuate said control valves, saidfurther stops being so disposed that operation of each actuatingcylinder is gradually retarded as its respective boom approaches a fullylowered or fully elevated condition.

5. Access equipment according to claim 4, wherein said further stops arecarried by two further linearly reciprocable members, each normallymaintained in a non-operative position and movable only when itsassociated boom approaches a fully lowered or elevated position.

6. Access equipment according to claim 5, wherein one of said members isthus moved by a pair of spaced abutments attached to the meansassociated with one of said booms.

7. Access equipment according to claim 5, wherein one of said members isthus moved by a pair of spaced abutments mounted on a pivotable armconnected to the means associated with one of said booms.

8. Access equipment according to claim 1, wherein the means associatedwith said first boom is constituted by a levelling rod forming part of aparallelogram levelling linkage of which the other part is constitutedby said first boom.

9. Access equipment according to claim 1, wherein the means associatedwith said second boom is constituted by a rod connected via a linkage tothe ram of the hydraulic actuating cylinder for said second boom.

10. Access equipment according to claim 1, wherein said means, saidstops and said control valves are all disposed on said first boomadjacent the lowermost end thereof.

11. Access equipment according to claim 10, wherein said control valvesare manually operable and connected for simultaneous operation toduplicate control valves provided on a cage or working platform at theuppermost end of the boom structure.

j i l l UNITED STATES PATENT AND TRADEMARK OFFICE QE EQ'HGN 'HICATE P COPATENT NO. 3,891,056

DATED June 24, 1975 INVENTOR(S) I DENIS HENRY ASHWORTH It is certifiedthat error appears in the aboveidentified patent and that said LettersPatent are hereby corrected as shown below:

Column 6, after claim 11, the last claim was omitted.

Insert the last claim to read as follows:

l2. Access equipment as defined in claim 1 wherein said first boom ispivotally mounted on a turntable on said supporting structure.-

this

S irred and RUTH C. MASON Arresting Officer C. MARSHALL DANN(mnmissiuncr uflaltnls and Trademarks

1. Access equipment comprising an articulated boom structure comprisinga first boom pivotally mounted at one end on a vehicle or likesupporting structure and at least a second boom pivotally connected tothe free end of said first boom, hydraulic actuating cylinders connectedfor effecting pivoting movement of the second boom relative to the firstboom and both booms relative to said supporting structure, controlvalves for said cylinders, movably mounted stops for controllingactuation of said valves, and means associated with each of said boomsand movable therewith for transmitting movements thereof individuallyand collectively to said stops to actuate said control valves, saidstops being so arranged that in response to movements of said booms andin accordance with permitted degrees of pivotal movement thereofoperation of said actuating cylinders is controlled as appropriate toprevent the boom structure assuming a potentially unstableconfiguration.
 2. Access equipment according to claim 1, wherein saidmeans comprise a pair of members each reciprocable substantiallylinearly in response to clockwise and anti-clockwise pivoting movementsrespectively of its associated boom, said stops being carried by afurther member also movable substantially linearly and operativelyconnected to said pair of members, the position of said further memberbeing at all times representative of the combined linear positions ofsaid pair of members.
 3. Access equipment according to claim 2, whereinthe members of said pair are adapted for relative movement in oppositedirections upon simultaneous raising or lowering of both of said booms,said further member being pivotally connected to a common memberextending between and pivotally connected to said pair of members, suchthat movements of said further member are at all times representative ofthe sum of the movements of said pair of members.
 4. Access equipmentaccording to claim 1, wherein said means are so movable with said boomsthat movements thereof are transmitted to further stops which aremovable to actuate said control valves, said further stops being sodisposed that operation of each actuating cylinder is gradually retardedas its respective boom approaches a fully lowered or fully elevatedcondition.
 5. Access equipment according to claim 4, wherein saidfurther stops are carried by two further linearly reciprocable members,each normally maintained in a non-operative position and movable onlywhen its associated boom approaches a fully lowered or elevatedposition.
 6. Access equipment according to claim 5, wherein one of saidmembers is thus moved by a pair of spaced abutments attached to themeans associated with one of said booms.
 7. Access equipment accordingto claim 5, wherein one of said members is thus moved by a pair ofspaced abutments mounted on a pivotable arm connected to the meansassociated with one of said booms.
 8. Access equipment according toclaim 1, wherein the means associated with said first boom isconstituted by a levelling rod forming part of a parallelogram levellinglinkage of which the other part is constituted by said first boom. 9.Access equipment according to claim 1, wherein the means associated withsaid second boom is constituted by a rod connected via a linkage to theram of the hydraulic actuating cylinder for said second boom.
 10. Accessequipment according to claim 1, wherein said means, said stops and saidcontrol valves are all disposed on said first boom adjacent thelowermost end thereof.
 11. Access equipment according to claim 10,wherein said control valves are manually operable and connected forsimultaneous operation to duplicate control valves provided on a cage orworking platform at the uppermost end of the boom structure.